1. Field of the invention
The present invention relates generally to an image forming apparatus, and more particularly to an image forming apparatus allowing the optional mounting of an appropriate peripheral device to the sizes and quantity of sheets to be copied and other factors, wherein the necessity of a particular peripheral device is assessed by an optional information system. The automatic document feeder will be referred to as "ADF".
2. Description of the prior art
Recently, users want image forming apparatus such as copying machines and printing machines that save labor and time, and users want to purchase peripheral devices by their own option. However, the users' option is arbitrary and may vary from operator to operator. In addition, the necessity of employing these peripheral devices is sometimes wrongly assessed, thereby leading to the purchase of inappropriate peripheral devices.
Peripheral devices includes an ADF, cassettes and sorters. A typical example is an ADF which is very much appreciated for its convenience. The ADF automatically copies originals stacked on a tray, so that it eliminates the bother of manually changing the originals. Owing to the use of an ADF the operator can do other works during the copying.
Another example is a cassette, which stores sheets and then automatically feeds them. Conventional cassettes are prepared in number corresponding to sizes of sheets to be stored, and users must have plural cassettes so as to copy A4, B4, B5 or other size sheets, and attach the necessary cassette to a copying machine or to a printing machine. Some sheet sizes are more often used than others, and some sheet sizes are rarely used at all. Variations in the frequency of use affect the capacity of a required cassette. A cassette must have a larger capacity if it stores sheets of the most frequently used size. On the other hand, if the sheets are of rarely used size, the sheets should not remain in the cassette for a long period of time, otherwise they would deteriorate owing to exposure to air.
A further example is a sorter, which separates copied sheets into groups; for example, when an original of 10 leaves or 10 serial pages is copied into 5 copies, each copy is discharged onto a different tray by the sorter. The sorter saves the bother of separating copied sheets into 5 groups ready for use, such as stapling the sheets into a booklet.
There are at least three methods for assessing the necessity of employing a particular peripheral device, which are as follows:
(1) When an original or originals are copied, the original platen is normally covered with a cover, except when a book is being copied, so as to avoid the movement of the original or the formation of blackened edges on the copied sheet during copying. When the originals are changed leaf by leaf, the cover must be opened and closed by hand. When many leaves are to be copied at one time the operator must repeat the opening and closing of the cover. If the operator must do it over a certain period of time, an ADF should be employed to save the labor and time. Thus, the employment of an ADF is justified.
(2) Another method comprises counting the frequency of turning on a switch for initiating the copying, hereinafter referred to as "print switch". More specifically, when originals are changed leaf by leaf, the turning on and off of the print switch must be repeated. By counting how many times the print switch has been turned on for a predetermined period of time, the frequency of changing originals (leaves) can be determined.
(3) A third method is to count time intervals in the previous copying operation. When the originals are changed leaf by leaf, the operation is stopped, and then starts. The whole operation is carried out at certain time intervals. When the time intervals are short, it shows that many originals are continuously copied.